Embryo Project Encyclopedia

David Michael Rorvik is a science journalist who publicized advancements in the field of reproductive medicine during the late twentieth century. Rorvik wrote magazine articles and books in which he discussed emerging methods and technologies that contributed to the progression of reproductive health, including sex determination, in vitro fertilization, and human cloning. During that time, those topics were controversial and researchers often questioned Rorvik’s work for accuracy. Rorvik contributed to the field of reproductive medicine by communicating methods of reproductive intervention and contributing to the controversy around new developmental medicine technologies.

In 1973, Ronald Ericsson developed the Ericsson method, which is a technique used to separate human male sperm cells by their genetic material. Ericsson, a physician and reproduction researcher, developed the method while conducting research on sperm isolation in Berlin, Germany, in the early 1970s. He found that the sperm cells that carry male-producing Y chromosomes move through liquid faster than the cells that carry female-producing X chromosomes. As a result of his findings, Ericsson suggested suspending a semen sample in a viscous liquid made from albumin protein, and collecting only sperm that quickly pass through the liquid. Shortly after Ericsson described his method, researchers demonstrated that it was effective for sex selection. However, later studies contested those results. Despite that, the Ericsson method is still utilized by couples in 2018 as a means of sex selection and was the first sperm separation technique used in combination with artificial insemination to enable people to select the sex of their children.

In the 1960s in the United States Landrum B. Shettles developed the Shettles method, which is a procedure for couples to use prior to and during an intercourse to increase their chances of conceiving a fetus of their desired sex. Shettles, a physician, who specialized in obstetrics and gynecology, found a difference in the size and shape of male sperm cells that he correlated with the different sex chromosomes they carry. Based on that finding, Shettles developed procedures for couples to follow based on whether they desire a female or a male fetus and published them in the 1970 book, Your Baby’s Sex: Now You Can Choose. The Shettles method is based on the idea that male-producing sperm prefer alkaline conditions, whereas female-producing sperm prefer acidic conditions. The method provides couples with a procedure intended to enhance the favored environment for the sperm that will supposedly produce the desired sex, including female douches to be used before intercourse and how to time sexual intercourse within the female menstrual cycle. The book Your Baby’s Sex: Now You Can Choose, made the Shettles method a widely popular method of natural sex selection.

Roger Wolcott Sperry studied the function of the nervous system in the US during the twentieth century. He studied split-brain patterns in cats and humans that result from separating the two hemispheres of the brain by cutting the corpus callosum, the bridge between the two hemispheres of the brain. He found that separating the corpus callosum the two hemispheres of the brain could not communicate and they performed functions as if the other hemisphere did not exist. Sperry studied optic nerve regeneration through which he developed the chemoaffinity hypothesis. The chemoaffinity hypothesis stated that axons, the long fiber-like process of neurons, connect to their target cells through special chemical markers. This challenged the previously accepted resonance principle of neuronal connection. Sperry shared the 1981 Nobel Prize in Physiology or Medicine with David Hubel and Torsten Wiesel.

In the 1950s and 1960s, Roger Sperry performed experiments on cats, monkeys, and humans to study functional differences between the two hemispheres of the brain in the United States. To do so he studied the corpus callosum, which is a large bundle of neurons that connects the two hemispheres of the brain. Sperry severed the corpus callosum in cats and monkeys to study the function of each side of the brain. He found that if hemispheres were not connected, they functioned independently of one another, which he called a split-brain. The split-brain enabled animals to memorize double the information. Later, Sperry tested the same idea in humans with their corpus callosum severed as treatment for epilepsy, a seizure disorder. He found that the hemispheres in human brains had different functions. The left hemisphere interpreted language but not the right. Sperry shared the Nobel Prize in Physiology or Medicine in 1981for his split-brain research.

In the book Your Baby’s Sex: Now You Can Choose, David Michael Rorvik and Landrum Brewer Shettles describe methods that couples can use prior to and during conception that will increase the chances of producing a child of their desired sex. Rorvik, a science writer, and Shettles, an obstetrics and gynecology researcher and physician, co-wrote the book. Shettles developed the methods detailed in the book during the 1960s. Although the authors claim a high success rate, some researchers have contested the validity of the methods proposed in Your Baby’s Sex: Now You Can Choose. Despite contradicting evidence for the effectiveness of the methods, the book itself has remained popular throughout its forty consecutive years in print. Since its original publication, Your Baby’s Sex: Now You Can Choose has reached a large audience, with over 1.5 million copies of the book sold worldwide, while adding to the controversy about the ethics of sex selection research.